The present invention relates to a light-sensitive composition and more specifically to a new photopolymerizable light-sensitive composition having high sensitivity and stability.
There has conventionally been tried to use a variety of reactive binders for the purpose of enhancing the sensitivity of light-sensitive compositions. For instance, many reactive binders whose side chains carry (meth)acrylate groups have been proposed. Examples thereof are disclosed in, for instance, Japanese Patent Publication for Opposition Purpose (hereinafter referred to as "J. P. KOKOKU") Nos. Sho 39-19898, Sho 51-37316 and Sho 49-17874 and U.S. Pat. No. 3,556,793.
These binders ensure such enhancement in the sensitivity of light-sensitive compositions, but they suffer from a problem of low storage stability. This makes it difficult to practically use them.
On the other hand, if a light-sensitive composition comprising a binder, a monomer and a photopolymerization initiator as disclosed in J. P. KOKOKU No. Sho 46-32714 is used for preparing a presensitized plate for use in making a lithographic printing plate (hereunder referred to as "PS plate"), it is found that the sensitivity of the PS plate is greatly influenced by the surface temperature thereof during imagewise exposure to light (hereunder this phenomenon is referred to as "temperature dependency"). Moreover, it is also found that the photopolymerizable composition undergoes post-polymerization after completion of imagewise exposure due to residual active species and its sensitivity increases as the time elapsed from the end of the imagewise exposure till the initiation of its development increases (hereunder this phenomenon is referred to as "latent image sensitization").
To solve the problems of the aforementioned storage stability, temperature dependency and latent image sensitization, Japanese Patent Unexamined Publication (hereunder referred to as "J. P. KOKAI") No. Sho 59-46643 (U.S. Pat. No. 4,511,645) proposes the use of binders each having an allyl group. These binders makes it possible to eliminate the foregoing problems and to impart high sensitivity to light-sensitive compositions and thus they have been practically used. However, there is a need for further enhancement of the sensitivity of light-sensitive compositions.